Semester

Fall

Date of Graduation

2001

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Physiology, Pharmacology & Neuroscience

Committee Chair

Dale L. Birkle.

Abstract

Chronic, inescapable stress during pregnancy (i.e. prenatal stress) modifies the behavior of the adult offspring. Several behaviors were evaluated in adult prenatally stressed (PS) rats, most notably the acoustic startle response and behavioral inhibition (i.e. freezing). PS rats do not differ in baseline peak startle responding, or in the habituation of the peak startle response when compared to the non-prenatally stressed (CON) rats. However, PS rats have greater peak responses and longer latencies to reach the peak response following systemic doses of the 5-HT 1A agonist, 8-OH-DPAT, compared to CON rats. The PS rats had shorter latencies than the CON rats under vehicle treatment.;In fear-potentiated startle testing, peak startle responding did not reach the same levels in the PS rats as it did in the CON rats; thus, it was inhibited. Latencies were depressed during fear-potentiated startle testing compared to baseline testing, and the PS rats had generally shorter latencies than the CON rats. Additionally, the latency was more sensitive to context after the training, demonstrating a decrease during the leader trials of the test session, before the increase in peak startle was noted during the testing trials. In defensive freezing, PS rats displayed more freezing following acute footshock and 24 hours later in the same context when the footshock was not presented. Rears were markedly attenuated immediately post-shock and, the next day, and only recovered significantly in the CON rats.;The data presented are consistent with PS rats being more reactive to fear provoking stimuli. The ramifications of this are discussed in terms of the neural circuitry that underlie the behaviors with possible changes that might be induced by prenatal stress. Additionally, some observations regarding the contextual influence on the acoustic startle response and freezing are discussed. Finally, several pieces of evidence are presented demonstrating that gross developmental and some neurochemical parameters of PS rats are indistinguishable from CON rats from birth to adulthood suggesting that source of the behavioral differences noted above is subtle in nature.

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